I have no idea who Nathan Cofnas is and what he's said or done, except for what was reported in the press, particularly in Retraction Watch (where I first read about Jason Arday, following a link from HN).What I can tell with some certainty is that, once again, in UK academia, the person blowing the whistle on plagiarism is the one facing consequences whereas the plagiarist has the full support of the academic establishment.
It is an enduring scandal of British academia that misconduct goes unpunished, swept under the rug, ignored and whitewashed. Liverpool John Moores University which had awarded Jason Arday's PhD carried out an investigation that found that copying another academic's work and submitting it under his own name was nothing but an "honest and reasonable error", not deliberate plagiarism, and "well within the accepted range of compliance with the academic standards of the time" [1].
It is also typical that Jason Arday himself did not contest the fact of plagiarism: he only sought to excuse it by shifting the blame to others: "Arday did not dispute the allegations of plagiarism, but said he had not received adequate supervision given his autism and learning disabilities, and described the allegations against him as being part of an "insidious and relentless" strategy to undermine black academics." (ibid).
This, too, is a recurring pattern with plagiarists: because the facts of the matter are often so blatantly obvious for all to see that pretending they didn't happen is too much even for academic integrity panels to ignore, the plagiarists tacitly accept the facts but seek to contest their meaning. And academia, ever fearful of scandal, duly complies.
The first victim of all this is nothing else but the quality of scholarship. If plagiarism is normalised, always treated with impunity, what else can be the result? Second-hand, stolen scholarship is shoddy scholarship.
[1] https://en.wikipedia.org/wiki/Jason_Arday#Initial_concerns